The policy, known colloquially as "Don't Ask, Don't Tell" (DADT), is a fudge introduced in the Clinton era to get around the fact that the US does not permit homosexuals to serve openly in the military. The armed forces of Canada, the entire EU, Australia, Israel and even Taiwan and South Africa have allowed openly gay service members for many years. The US stands alone with Turkey in forbidding it, ostensibly on the grounds that the presence of gays in the armed forces "would create an unacceptable risk to the high standards of morale, good order and discipline, and unit cohesion that are the essence of military capability".
DADT created a bizarre situation in that the armed forces recognised that there were gays in the military, but sought to prevent them from being discharged (which they were obliged to do) by introducing a kind of "see no evil, hear no evil, speak no evil": as long as servicemen and -women were not questioned about their sexual orientation or talked about it with fellow soldiers, the fact was ignored. Any that did were discharged immediately, albeit honourably.
Forced to make a decision on the matter by a court order that temporarily lifted DADT, politicians in Washington spent much of this year wrangling over the issue. A subsequent poll found that 72% of servicemen said they wouldn't have any problems serving alongside gays, lesbians and transsexuals. Although mainly Republicans staged repeated filibusters in an attempt to talk the issue to death, the repeal of DADT - and with it the ban on gays in the US military - was finally approved by the Senate this week, and the National Defense Authorization Act has now arrived on President Obama's desk.
Welcome to the 20th century, America.